Dynamical Degree of Crystallinity of Partially Crystalline Polymers

1963 ◽  
Vol 18 (1) ◽  
pp. 124-131 ◽  
Author(s):  
Riichirô Chûjô
Keyword(s):  
Degree Of Crystallinity ◽  
Crystalline Polymers ◽  
Dynamical Degree

Prediction of crystallinity profile and eject time of injection molded parts using finite element method (FEM)

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Mehdi Mostafaiyan ◽  
Farhad Sharif
Keyword(s):  
Finite Element ◽  
Degree Of Crystallinity ◽  
Element Analysis ◽  
Melt Temperature ◽  
Crystalline Polymers ◽  
Molded Parts ◽  
Time Part ◽  
Injection Molded ◽  
The Subject

AbstractQuality of injection molded parts of semi-crystalline polymers has been the subject of intense interest from both analytical and industrial points of view. Crystallinity profile plays an important role in determining mechanical properties of a part and its quality. Therefore it is important to analyze the effect of injection molding parameters on the crystallinity profile of the molded parts. In this study, finite element analysis has been used to solve the equations of mass, momentum, and energy conservation simultaneously with the equation of crystallization kinetics to predict melt front, its solidification and crystallinity profile. The results from our numerical analysis have been compared with the reported experimental results. Furthermore, progress of the crystallization is proposed to be a proper criterion for estimation of the eject time. Finally, the effects of mold and melt temperature on the eject time; part temperature and average degree of crystallinity, for a specific compound are also presented.

scholarly journals Thermotropic Liquid Crystalline Polymers with Various Alkoxy Side Groups: Thermal Properties and Molecular Dynamics

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 992 ◽  
Author(s):  
Gi Tae Park ◽  
Jin-Hae Chang ◽  
Ae Ran Lim
Keyword(s):  
Molecular Dynamics ◽  
Thermal Properties ◽  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Magic Angle Spinning ◽  
Degree Of Crystallinity ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Crystalline Polymers ◽  
Thermotropic Liquid Crystalline Polymers

Two series of thermotropic liquid-crystalline polymers (TLCPs) were synthesized by reacting various dialkoxy terephthalate units with hydroquinone (HQ) and 2,6-naphthalene diol (Naph). The dialkoxy terephthalate moieties used in this study include 2,5-diethoxyterephthalate, 2,5-dibutoxyterephthalate, and 2,5-dihexyloxy-terephthalate. All the TLCPs synthesized in this study formed nematic phases. The molecular motions according to the length of the dialkoxy side groups in the TLCPs were evaluated by 13C cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopy. The thermal properties and molecular dynamics of the TLCPs are found to be affected by the length of the dialkoxy side group and the aromatic diol unit in the main chain. Further, the thermal behaviors, liquid crystalline mesophases, and degree of crystallinity of the two series of TLCPs, i.e., HQ- and Naph-TLCPs, are compared.

scholarly journals Image analysis as a useful tool for fast detection of dimensional and structural changes of poly(ethylene terephthalate) containers

2018 ◽  
Vol 72 (6) ◽  
pp. 351-361
Author(s):  
Nenad Jevremovic ◽  
Sava Velickovic ◽  
Melina Kalagasidis-Krusic ◽  
Vesna Panic ◽  
Tatjana Volkov-Husovic ◽  
...  
Keyword(s):  
Image Analysis ◽  
Structural Changes ◽  
Ethylene Terephthalate ◽  
Degree Of Crystallinity ◽  
Crystalline Polymers ◽  
Fast Detection ◽  
Poly Ethylene Terephthalate ◽  
One Step ◽  
Poly Ethylene ◽  
Continuous Material

The aim of this paper is to present image analysis as a useful technique for fast, reliable and non-destructive detection of dimensional and structural changes in polymers. The possibility of applying image analysis was demonstrated in the case of solvent-induced crystallization of poly(ethylene terephthalate) (PET) containers filled with commonly used organic solvents: chlorobenzene, isophorone, xylene, Espesol, Shellsol A 100, Solvesso 150, propylene glycol, glycerin and water and subjected to the storage stability test at 54 ?C for 14 days (CIPAC 1-MT 46.1.3). In addition, the obtained results were analyzed using one-step analysis of variance (ANOVA) combined with the Duncan?s statistical test (p<0.05). According to the achieved results, three main impacts of the presented paper could be distinguished: 1) dimensional and transparency changes could be precisely followed by image analysis in both following cases: for small changes in water, as well as for significant ones in chlorobenzene; 2) a correlation between the changes in the degree of crystallinity and transparency could be obtained without the continuous material testing by DSC; 3) image analysis is potentially applicable for assessment of other crystalline polymers.

An Electron Microscopic Study Of Some Solid-State Polymerization Reactions

1977 ◽  
Vol 35 ◽  
pp. 170-171
Author(s):  
William Jones ◽  
John M. Thomas ◽  
David A. Livesley
Keyword(s):  
Molecular Weight ◽  
Solid State ◽  
Perfect Crystal ◽  
Degree Of Crystallinity ◽  
Electron Microscopic ◽  
Crystalline Polymers ◽  
Transmission Electron ◽  
Organic Solid ◽  
High Degree ◽  
Molecular Weight Product

There is interest at present amongst organic solid-state chemists in producing, through topochemical reaction, stereoregular and crystalline polymers of high molecular weight. In certain reactions the geometry of the polymer product and the high degree of crystallinity are completely determined by the molecular packing in the monomer crystal (1). In others, however, low molecular weight product or products not predicted from a knowledge of the monomer packing have lead to suggestions that dislocations or other regions of imperfection may be important as sites of initiation of reaction or possibly of nucleation of the formed polymer (2). Defects will also control the length of the formed polymer (2).We have utilized transmission electron microscopy for investigating defects in anthracene and some of its derivatives, which also undergo chemical and photo-induced reactions, occasionally in a manner not determined by the perfect crystal lattice (3). Consequently we felt it appropriate to observe by TEM foils of monomer before, during and after polymerization.

Structure-property relations of liquid crystalline polymers

1987 ◽  
Vol 45 ◽  
pp. 460-463
Author(s):  
Linda C. Sawyer
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Structural Model ◽  
Crystalline Polymer ◽  
Liquid Crystalline Polymers ◽  
Mechanical Anisotropy ◽  
Structure Property ◽  
Preparation Methods ◽  
Crystalline Polymers ◽  
Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

SEM/FESEM imaging of lamellar structures in melt extruded polyethylene films

1992 ◽  
Vol 50 (2) ◽  
pp. 1142-1143
Author(s):  
R.T. Chen ◽  
M.G. Jamieson ◽  
R. Callahan
Keyword(s):  
Imaging Techniques ◽  
Membrane Surface ◽  
High Stress ◽  
Extrusion Direction ◽  
Polymeric Membranes ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Crystalline Polymers ◽  
Lamellar Structures ◽  
Resolution Imaging

“Row lamellar” structures have previously been observed when highly crystalline polymers are melt-extruded and recrystallized under high stress. With annealing to perfect the stacked lamellar superstructure and subsequent stretching in the machine (extrusion) direction, slit-like micropores form between the stacked lamellae. This process has been adopted to produce polymeric membranes on a commercial scale with controlled microporous structures. In order to produce the desired pore morphology, row lamellar structures must be established in the membrane precursors, i.e., as-extruded and annealed polymer films or hollow fibers. Due to the lack of pronounced surface topography, the lamellar structures have typically been investigated by replica-TEM, an indirect and time consuming procedure. Recently, with the availability of high resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM), the microporous structures on the membrane surface as well as lamellar structures in the precursors can be directly examined.The materials investigated are Celgard® polyethylene (PE) flat sheet membranes and their film precursors, both as-extruded and annealed, made at different extrusion rates (E.R.).

Factors affecting microstructural scale in liquid crystalline polymers

1990 ◽  
Vol 48 (4) ◽  
pp. 220-221
Author(s):  
Christine M. Dannels ◽  
Christopher Viney
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Factors Affecting ◽  
Crystalline Polymers ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Lower Viscosity ◽  
Fine Microstructure ◽  
Planar Orientation ◽  
Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

Quantitative high-resolution electron microscopy (HREM) of defects in ordered polymers

1996 ◽  
Vol 54 ◽  
pp. 166-167
Author(s):  
Patricia M. Wilson ◽  
David C. Martin
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Liquid Crystalline ◽  
High Resolution Electron Microscopy ◽  
Polymer Materials ◽  
Scattered Electron ◽  
Crystalline Polymers ◽  
Resolution Electron ◽  
Beam Damage

Efforts in our laboratory and elsewhere have established the utility of low dose high resolution electron microscopy (HREM) for imaging the microstructure of crystalline and liquid crystalline polymers. In a number of polymer systems, direct imaging of the lattice spacings by HREM has provided information about the size, shape, and relative orientation of ordered domains in these materials. However, because of the extent of disorder typical in many polymer microstructures, and because of the sensitivity of most polymer materials to electron beam damage, there have been few studies where the contrast observed in HREM images has been analyzed in a quantitative fashion.Here, we discuss two instances where quantitative information about HREM images has been used to provide new insight about the organization of crystalline polymers in the solid-state. In the first, we study the distortion of the polymer lattice planes near the core of an edge dislocation and compare these results to theories of dislocations in anisotropic and liquid crystalline solids. In the second, we investigate the variations in HREM contrast near the edge of wedge-shaped samples. The polymer used in this study was the diacetylene DCHD, which is stable to electron beam damage (Jc = 20 C/cm2) and highly crystalline. The instrument used in this work was a JEOL 4000 EX HRTEM with a beam blanidng device. More recently, the 4000 EX has been installed with instrumentation for dynamically recording scattered electron beam currents.

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